<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        *{
            margin: 0;
            padding: 0;
        }
        #app{
            position: absolute;
            right: 100px;
            bottom: 100px;
            width: 200px;
            height: 200px;
            background: pink;
        }
    </style>
</head>
<body>
    123
    <div id="app">

    </div>
</body>
</html>